Calculating gas pressure at a changing system

Povilas

Hello, I'm having a problem calculating the final pressure before condenser. I'm calculating the pressure that builds up in a system that at the beginning has atmospheric pressure @ T=20C and is introduced with 1 mole/second of CO2(44.01g/mol) @ T=60C and 0.318 mole/second of CH2Cl2(84,93 g/mol) @ T=60C. The volume of the system is 80 m3. There is an outlet after the condenser. The amount of gases that enters the system must exit trough the condenser. So I think there should be a constant pressure at some point. The process goes for 360 minutes. I have very little understanding of gas mechanics, I would be grateful for ant help.

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Chestermiller

Mentor
Is there an exact statement of this problem? If so, please provide it?

• Povilas

Povilas

Is there an exact statement of this problem? If so, please provide it?
There is no exact statement but my goal is to calculate all the parameters needed to choose a condenser that can reclaim most of the CH2Cl2.

Povilas

This problem is about gas exiting polyurethane foam during its production. The production line is sealed so all the gases are trapped inside.
Every second foam releases:
1 mole of CO2(44.01g/mol) @ T=60C
0.318 mole of CH2Cl2(84,93 g/mol) @ T=60C
The final goal is to calculate the required condenser to reclaim CH2Cl2.
the volume of the production line is 80m3
I will add diagram and some calculations that i tried soon

• Chestermiller

Povilas

I tried to calculate the temperature and how fast does CH2Cl2 replace air in the system.

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Povilas

3320 is moles of air inside the system, 79.08 is moles of CO2/CH2Cl2
every line is +1 min but i think all of these calculations are wrong.

Povilas

First i calculated moles of air inside the system, then i tried to calculate under the assumption that if the system gains n*T of energy it should lose the same amount. But i think this is wrong assumption. Then I calculated the amount of n(air)* T1 and n(CO2/CH2Cl2)*T2 and how fast does CO2/CH2Cl2 replace air.
I don't really know where to begin. I will be thankful for any help. :)

Last edited:

Povilas

The main thing I need is to understand how to calculate the maximum pressure that can develop inside the system. As I understand the gases that exit the foam increase the pressure, but at the same time some gases exit the system trough condenser decreasing the pressure.

Chestermiller

Mentor
To do this, you need to know the pressure-drop / flow-rate relationship for the condenser. You may have to measure that.

What is that brown thing in the figure? What is that rectangular box between the big box on the bottom and the condenser?

• Povilas

Povilas

To do this, you need to know the pressure-drop / flow-rate relationship for the condenser. You may have to measure that.

What is that brown thing in the figure? What is that rectangular box between the big box on the bottom and the condenser?
It's foam pattern or rise. Thank you i will look into pressure-drop / flow-rate relationship for the condenser.

"Calculating gas pressure at a changing system"

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